1. Field of the Invention
The present invention relates to light intensifiers, particularly to devices for focusing down a beam of light to produce a smaller beam with a greater intensity, and more particularly to a hollow lensing duct for intensifying light using a combination of front surface lensing and reflective waveguiding.
2. Description of Related Art
Traditionally, solid optically pumped lasers consist of a solid material where the optical gain in the material is generated by stimulated emission. The laser rod was initially optically pumped by a flash lamp or an arc source, which was generally inefficient and the heat generated by the pumping means sometimes damaged the laser rod.
In an effort to develop more efficient solid state lasers which generate higher output power and have a longer life time, the use of lateral pumping means, such as solid state laser diode arrays that are mounted on the side of a laser slab, was initiated. Various approaches for efficient transfer of the energy from the diode arrays to the solid laser rod or slab have been developed, which include the use of reflective coatings, optical waveguides, collimating lenses, and prisms.
One of the existing problems associated with the use of large diode arrays to pump lasing material is effectively concentrating the light from a diode array onto the laser slab or rod. U.S. Pat. No. 5,307,430, directed to a lensing duct, provided a solution to that problem by condensing and increasing the intensity of pump light from a diode array onto a solid laser rod by a combination of front surface lensing and reflective waveguiding via a lensing duct constructed from inexpensive glass or plastic.
More specifically. U.S. Pat. No. 5,307,430 is directed to a lensing duct that condenses/intensifies light by using a combination of front surface lensing and reflective waveguiding. The patent discloses a wider, lens-shaped input side coated with an antireflective coating, four uncoated side surfaces that use total internal reflection to prevent light from escaping, and a narrower output side. The patent does not disclose the use of a hollow structure for that portion of the lens duct that serves to confine the light by total internal reflection in combination with a front lens containing a hole.
The solid lens ducts, described in U.S. Pat. No. 5,307,430, which is incorporated herein by reference, are optical devices that have found application in the coupling of pump radiation from extended two-dimensional semiconductor laser diode arrays into solid-state laser gain media. The operation of these devices relies on the combined effects of lensing at the curved input surface and channeling by total internal reflection off the canted sides. These devices are fabricated out of a single piece of transparent optical material. One drawback of the patented lens duct, in certain situations, is that it obstructs access to the end of the laser rod or slab and so requires the high-reflector-laser coating to be applied directly to the end of the rod or slab.